3. (15 pts) Under conditions in which a cell is depending on catabolism of amino

Question

3. (15 pts) Under conditions in which a cell is depending on catabolism of amino acids for energy, a ketoglutarate enters the citric acid cycle. a) Wh ere does catabolism of amino acids occur and where does the citric acid cycle occur? insole the iner membraru h mituchonda b) What amino acid is used as a source of NH3' group for amine transfer reactions? c) What are the subsequent reactions that a ketoglutarate will undergo? d) Why would there be a build-up of oxaloacetate? e) What steps would be needed to make oxaloacetate available for gluconeogenesis?

Explanation / Answer

3. Normally human body uses glucose as an energy source which is a carbohydrate, when body runs out of glucose it starts using fats, so after all the fats are consumed then only proteins or amino acids are used as energy source. So under starvation conditions when none other source of energy is available then, amino acids are used as a source of energy.

b) All amino acids have amine group attached, so anyone can be used for amine transfer reactions.

c) alpha ketoglutarate is converted into succinyl coenzyme A by converting NAD+ into NADH. CO2 is released and the reaction takes place in presence of enzyme alpha ketoglutarate dehydrogenase.

e) Phosphoenol pyruvate carboxykinase enzyme converts oxaloacetate into Phosphoenol pyruvate which then can begin gluconeogenesis.

Phosphoenol pyruvate can be converted into pyruvate by enzyme pyruvate kinase. Pyruvate then gets converted into Acetyl Coenzyme A which can enter gluconeogenesis pathway.

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